<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    *{
        margin: 0;
        padding: 0;
    }
    .box{
        background: #888;
        height: 10%;
        margin-left: 50px;
    }
    .left{
        background: rgb(56,202,15);
        opacity: 0.5;
        border: 3px solid rgb(252,155,21);
        width: 200px;
        height: 200px;
    }
    .right{
        background: rgb(235);
    }
</style>
<body>
    <div class="box">
        <div class="left"></div>
        <div class="right"></div>
    </div>
</body>
</html>